The present invention relates to methods of providing organ/tissue-specific functions to a subject by transplantation of developing organs. More particularly, the present invention relates to methods of treating pancreatic, hematological/metabolic and pulmonary diseases in mammals by transplantation of developing xenogeneic/allogeneic porcine/human pancreatic, lymphoid/hematopietic or pulmonary organs/tissues, respectively.
Pancreatic diseases such as diabetes, hematological/metabolic diseases such as hemophilia A and Gaucher disease, and pulmonary diseases such as lung failure are diseases of great medical and economic impact for which no satisfactory/optimal treatments are available.
Diabetes is a debilitating and potentially lethal disease that develops in nearly 5 percent of the world's population. In the United States alone, an estimated 18 million people have diabetes mellitus, and each year about 1 million Americans aged 20 or older are diagnosed with the disease. It is the sixth leading cause of death in the US and is responsible for over 200,000 deaths a year. People with diabetes have a shortage of insulin or a reduced ability to use insulin, the hormone regulates blood glucose levels. In mammals the pancreas is responsible for the production and secretion of insulin. The standard therapy for diabetes, daily injections of insulin, does not satisfactorily prevent the debilitating and lethal consequences of this disease.
Pulmonary failure is a highly debilitating and potentially lethal affliction which can arise from numerous types of diseases, including cystic fibrosis, emphysema, pulmonary fibrosis or pulmonary hypertension. While lung transplantation may be employed as a last resort for treating such diseases, there is an insufficient supply of donor organs, with one quarter of the candidates dying on the waiting list and the limit for inscription being often set at 60 years of age. Postoperative mortality at two months is about 15 percent and is related to graft dysfunction, infection, bronchial complications. Five-year survival is still only about 50 percent.
The genetic defect causing hemophilia A affects about one in every 10,000 males. Due to the resultant clotting deficiency, those afflicted with the disease suffer severe bleeding episodes due to small injuries, internal bleeding, and joint hemorrhage, which leads to arthropathy, the major cause of morbidity in hemophilia. Normal levels of factor VIII average between 50 to 200 ng/ml of blood plasma (Mannucci, P. M. in Practical Laboratory Hematology, ed. Koepke, J. A., Churchill Livingstone, N.Y., pp: 347-371, 1990); however, patients suffering from mild to moderate hemophilia A typically have plasma levels well below 2-60 ng/ml, while levels below about 2 ng/mL result in severe hemophilia.
Treatment of hematological/metabolic diseases such as hemophilia A and Gaucher disease is generally effected via enzyme replacement therapy. However, enzyme replacement therapy has numerous significant disadvantages, including the need to administer the replacement enzyme via injection, a painful, inconvenient, and expensive process. The discontinuous dose administration of a replacement enzyme furthermore fails to achieve continuously adjusted physiological levels of the enzyme according to physiological need, as would be achieved by a normal enzyme producing cell population. Thus, enzyme replacement therapy of hematological/metabolic diseases fails in many cases to achieve satisfactory/optimal disease treatment.
Transplantation of fully differentiated haplotype-matched pancreatic or pulmonary grafts from postgestational stage donors is a life-saving, medical procedure of choice for replacing injured or diseased organs such as pancreas or lung. Such a treatment modality, however, suffers from considerable disadvantages. Allogeneic transplantation of differentiated pancreatic or pulmonary organs/tissues is impossible to implement in a great many cases due to the unavailability of suitable immunologically matched transplant donors. Furthermore, use of human donors to provide organs/tissues for transplantation often presents health risks and ethical dilemmas. Thus, large numbers of patients who would otherwise benefit from therapeutic transplantation succumb to diseases associated with pancreatic or pulmonary failure while awaiting matched transplant donors. Moreover, even when suitably haplotype matched transplant donors are found, permanent and harmful immunosuppressive treatments, such as daily administration of cyclosporin A, are generally required to prevent graft rejection. Use of drugs such as cyclosporin A may be undesirable but the benefit of a life saving transplant outweigh the risk of immunosuppressive treatment. Immunosuppressive therapy nevertheless is highly undesirable since these cause severe side effects such as carcinogenicity, nephrotoxicity and increased susceptibility to opportunistic infections. Immunosuppressive treatments contribute to the drawbacks of allogeneic transplantation since these are often unsuccessful in preventing rejection in the short term, and are generally incapable of preventing rejection in the long term. Acute rejection of transplanted grafts is often fatal.
An alternative to allograft transplantation involves xenograft transplantation, i.e., transplantation of animal-derived grafts, in particular porcine grafts, which are well established as a potential animal alternative to human grafts. The great advantages of using xenografts for transplantation are their availability on demand to all patients in need of transplantation, as well as avoidance of the medical and ethical burden of harvesting grafts from live or cadaveric human donors. However, to date, xenogeneic organ/tissue grafts have been ruled out for human transplantation due to their heretofore insurmountable immunological incompatibility with human recipients.
A potentially effective strategy for treating diseases resulting from or associated with abnormal activity of at least one biomolecule (e.g., monogenic, hematological, metabolic diseases) such as hemophilia A and Gaucher disease would involve non-syngeneic donor transplantation of lymphoid tissues/organs, such as spleen, which are potentially capable of generating therapeutic levels of different gene products such as factor VIII or glucocerebrosidase which are respectively deficient in such diseases. As described above, however, the state of the art of therapeutic transplantation generally remains associated with critical disadvantages.
Thus, in view of the unique potential curative benefits of transplantation therapy, there is clearly an urgent and longstanding need for non-syngeneic donor-derived pancreatic, pulmonary and lymphoid/hematopietic organs/tissues which can be obtained in sufficient quantities, and which are optimally tolerated immunologically, so as to render feasible the routine and optimally effective therapeutic transplantation of such organs/tissues.
One strategy, which has been proposed to fulfill this aim involves using gestational stage grafts for transplantation. Such an approach is promising since it has been shown that immunological tolerance to grafts derived from gestational stage tissue is better than that to grafts derived from adult stage tissues (Dekel B. et al., 1997. Transplantation 64, 1550; Dekel B. et al., 1997. Transplantation 64, 1541; Dekel B. et al., 1999. Int Immunol. 11, 1673; Hammerman M R., 2000. Pediatr Nephrol. 14, 513). Furthermore, the enhanced growth and differentiation potential of gestational stage grafts relative to differentiated grafts is highly desirable for generating optimally functional, host integrated grafts. For example, fetal pancreatic islet cells, such as insulin producing beta cells, display enhanced cell growth and differentiation relative to differentiated islet beta cells.
The potential of gestational stage porcine renal (Dekel B. et al., 2003. Nat Med 9:53-60; Hammerman M R., 2004. Am J. Transplant. 4 Suppl 6:14-24), pancreatic (Korsgren O. et al., 1991. Diabetologia 34:379-86; Beattie G M. et al., 1997. Diabetes 46:244-8; Fox A. et al., 2002. Xenotransplantation 9:382-92; Korbutt G S. et al., 1996. The Journal of Clinical Investigation 97:2119-29; Amaratunga A. et al., 2003. Xenotransplantation 10:622-7), hepatic (Kokudo N. et al., 1996. Cell Transplantation 5:S21-2; Takebe K. et al., 1996. Cell Transplant 5:S31-3), neuronal (Larsson L C. et al., 2001. Exp Neurol 172:100-14; Larsson L C. et al., 2003. Transplantation 75:1448-54; Armstrong R J. et al., 2002. Exp Neurol 175:98-111) grafts to generate functional organs/tissues following transplantation into non-syngeneic hosts has been extensively described. The potential of gestational stage human pulmonary (Angioi K. et al., 2002. The Journal of Surgical Research 102:85-94), cardiac or intestinal grafts (Angioi K. et al., 2002. The Journal of Surgical Research 102:85-94; Lim F Y. et al., 2003. Journal of Pediatric Surgery 38:834-9) to generate organs/tissues having organ-specific function following transplantation into non-syngeneic hosts has also been demonstrated.
Thus, various approaches have been described in the prior art for using developing pancreatic organ/tissue grafts for therapeutic transplantation.
For example, it has been shown that human fetal islets including the earliest insulin secreting cells, transplanted into nude mice and rats display continued growth and development, including production of the other pancreatic hormones: glucagon, somatostatin, and pancreatic polypeptide (Usadel et al., 1980. Diabetes 29 Suppl 1:74-9). Similarly, it has been shown that human embryonic pancreas-derived grafts transplanted into NOD/SCID mice, generated graft-derived insulin producing human beta-cells (Castaing M. et al., 2001. Diabetologia 44:2066). Gestational stage porcine islet transplants in mice may display a similar differentiation program, with similar timing, as the normal non-transplanted tissues.
Other examples include transplantation of gestational stage porcine islet cells in nude mice (Korsgren O. et al., 1991. Diabetologia 34:379-86; Otonkoski T. et al., 1999. Transplantation 68, 1674), of fetal pancreas in immunodeficient rodents (Fox A. et al., 2002. Xenotransplantation 9:382-92; Amaratunga A. et al., 2003. Xenotransplantation 10:622-7), of human fetal islets in nude mice and rats (Beattie G M. et al., 1997. Diabetes 46:244-8;) and of porcine fetal islet tissue into nude mice (Korbutt G S. et al., 1996. J Clin Invest. 97:2119-29). Another approach involves transplantation of fetal porcine islet-like cell clusters into cynomolgus monkeys (Soderlund J. et al., 1999. Transplantation 67:784-91). Still another approach involves intratesticular transplantation of neonatal porcine islets into non-immunosuppressed beagles (Gores P F. et al., 2003. Transplantation 75:613-8).
Additionally, attempts to transplant porcine fetal pancreatic tissues in diabetic human recipients have been made (Groth C G. et al., 1998. Transplantation Proceedings 30:3809-10; Groth C G. et al., 1999. J Mol. Med. 77, 153; Reinholt F P. et al., 1998. Xenotransplantation 5:222-5; Korsgren O. et al., 1992. Transplantation Proceedings 24:352-3; Groth C G. et al., 1994. Lancet 344:1402-4).
US 2003/0198628 to Hammerman discloses a method for pancreas transplantation comprising implanting into a host an embryonic pancreas. In one embodiment the pancreas is harvested from a porcine embryo from about day E20 to about day E38, the most preferred harvest day being about day E29.
US Patent Application Nos. 20040082064 and 20040136972 to some of the inventors of the present application suggest treating pancreatic disease in humans by transplantation of porcine pancreatic organ/tissue grafts at a developmental stage of 20-28 days of gestation, and teach that 27-28 days of gestation is the optimal gestational stage of any type of porcine organ/tissue grafts for therapeutic transplantation.
Various prior art approaches have been described in the prior art for using developing pulmonary organ/tissue grafts for therapeutic transplantation.
In one approach, human pulmonary grafts at a gestational stage of 6-10 weeks were transplanted into immunodeficient mice (Angioi K. et al., 2002. The Journal of Surgical Research 102:85-94).
In another approach, lung fragments from human fetuses at 10 to 14 weeks of gestation were transplanted into immunodeficient mice (Groscurth P, Tondury G., 1982. Anat Embryol (Berl). 165:291-302).
Regarding transplantation of lymphoid/hematopietic organ/tissue grafts, US Patent Publication No. 20040136972 to some of the inventors of the present application asserts that all types of porcine organ/tissue grafts at a developmental stage of 27-28 days, specifically including splenic organ/tissue grafts, are optimal for therapeutic transplantation.
However, all previous approaches involving transplantation of developing non-syngeneic pancreatic, pulmonary or lymphoid/hematopietic organs/tissues suffer from some or all of the following drawbacks:
(i) suboptimal tolerance by non-syngeneic host lymphocytes;
(ii) suboptimal structural and functional graft differentiation, for example with respect to insulin production by pancreatic organ/tissue grafts;
(iii) predominantly graft-derived, as opposed to host-derived, graft vascularization, thereby leading to immune rejection;
(iv) suboptimal growth;
(v) inadequate availability of transplantable organs/tissues; and/or
(vi) suboptimal safety for human administration, notably with respect to avoidance of generation of graft-derived teratomas.
Previous approaches employing developing non-syngeneic grafts have been uniformly suboptimal since the optimal gestation time for implantation based on risk for teratoma, growth potential and immunogenicity, all of which might vary between different organs in fetal development, was not sufficiently characterized.
There is thus a widely recognized need for, and it would be highly advantageous to have, a method of treating human diseases amenable to therapeutic transplantation by transplantation of developing non-syngeneic pancreatic, pulmonary or lymphoid/hematopietic organs/tissues devoid of the above limitations.